Oh didnt know there is thermal paste for GPUs as well as CPUs. I am not sure if i would know how and where to add it on. As for ventilation computer box has actually intake/exhaust ventilation sucking air at bottom and then exhausting it on upside creating airflow trough cards, but it doesnt help much since GPU temp goes straight to 95 on first minute of mining.
Yep, both cpu's and gpu's have thermal paste on their chips.
You can use this to see how to take the card apart and clean/repaste it
https://www.youtube.com/watch?v=XvD1s83u_hQThen just go in reverse order to put it back together.
Not always on the GPU, he needs to be careful that they did not use a pad, unless they have changed that practice.
Also, try open case first OP...with a fan blowing on it or whatever. Unless your wanting total silence, try this first.
You also have to think about the extra power your using for the WC system. Many of us are living on the edge getting as much watts/amps out of a PSU... adding WC will only add to the load.